Vacuum processing method

ABSTRACT

The vacuum processing device comprises vacuum processing chambers  30   a  and  30   b  for performing predetermined treatments to a wafer being transferred to a predetermined position within the chamber, an atmospheric transfer equipment  7  for transferring a wafer in atmospheric air to a vacuum transfer equipment  10,  a vacuum transfer equipment  10  disposed with in a vacuum transfer chamber  2  connecting the atmospheric air and said vacuum processing chambers for transferring the wafer received from said atmospheric transfer equipment to said predetermined position within said vacuum processing chamber, and wafer position sensors  11   a,    11   b,    11   c  and  11   d  disposed near the ingress path leading into said processing chambers for detecting the displacement of said wafers being transferred.

FIELD OF THE INVENTION

[0001] The present invention relates to a device and method for vacuumprocessing, and especially relates to a vacuum processing device andmethod capable of transferring wafers disposed in atmospheric air to apredetermined position within a vacuum processing chamber.

DESCRIPTION OF THE RELATED ART

[0002] Japanese Patent Application Laid-Open No. 8-172034 discloses avacuum processing device equipped with a display capable of displayingthe movement of to-be-processed bodies such as wafers on a screen inreal time. This device enables the operator to monitor the movement ofthe wafers etc. from the exterior of the vacuum processing device.

[0003] Though it is not clearly illustrated in the above-mentioneddocument, the vacuum processing chamber is usually equipped with aviewport, and the operator visually observes the wafers etc. fromoutside the vacuum processing device through the viewport in order toadjust the position of the wafers within the device.

[0004] Upon manufacturing semiconductor devices, it is common to treat asingle sample body (wafer) and then to cut the wafer into plural piecesto create plural parts. The wafer is generally circular, but in manycases the parts being manufactured by cutting the wafer are rectangular.The number of parts that can be produced from a single wafer isdetermined by how these rectangular parts are cut out from the circularwafer, which influences the productive efficiency greatly.

[0005] If the wafer is circular, the area per unit radial widthincreases as the diameter of the circle increases. Therefore, it isnecessary to collect parts as efficiently as possible from the outermostrim portion.

[0006] For example, upon processing wafers in a plasma etching device,the wafer stage on which the wafer is mounted is preferably smaller indiameter than the wafer to be processed so as to prevent damage causedby plasma. On the other hand, the wafer must be processed as preciselyas possible and the wafer temperature must be controlled throughout thewhole wafer surface. Thus, when considering only the latter requirement,the wafer stage is preferably larger in diameter than the wafer. Inorder to satisfy these two contradictory demands, the diameter of thestage must be smaller than the diameter of the wafer but at the sametime as large as possible. Moreover, the transfer accuracy fortransferring the wafer on to the stage is preferably as precise aspossible.

[0007] At first, the wafer is disposed in atmospheric air. Aftercentering or aligning the crystal orientation of the wafer, anatmospheric robot takes hold of the wafer and mounts the wafer forexample on a load lock. Then, a vacuum robot disposed within a vacuumtransfer chamber (buffer chamber) holds the wafer located in the loadlock chamber, and transfers the same to the next stage, such as into avacuum processing chamber. These steps are performed repeatedly.

[0008] Therefore, according to the wafer transfer procedure, aftercentering and aligning the orientation of the wafer, the step oftransferring the wafer using a robot onto a determined wafer stage andthe step of removing the wafer from the stage are performed repeatedly.The wafer is somewhat displaced every time the steps are repeated, andas the number of performed steps increases, the displacement(misalignment) is accumulated.

[0009] Conventionally, when correcting the displacement of the wafer(misalignment of the wafer on the wafer stage within a processingchamber) at the final stage, the operator adjusts the location of thearm of the transfer robot and the like based on visual observation.Recently, however, the designs of the processing devices have becomemore complex, and it has become difficult to form the viewport throughwhich the operator visually observes the displacement of the wafers at alocation that can be accessed easily by the operator. Even further,since it is very difficult for each operator to position his/her eyes atthe same determined position when visually observing the wafers, andsince the vision of each operator differs, there are differences in thedisplacement correction accuracy among the operators performing thetask.

SUMMARY OF THE INVENTION

[0010] The present invention aims at solving the above mentionedproblems of the prior art by providing a vacuum processing devicecapable of transferring the wafers with improved accuracy by detectingand correcting the displacement of the transferred wafer just prior tothe final stage.

[0011] The present invention adopts the following structure in order tosolve the above problems.

[0012] The present invention comprises a vacuum processing chamber forperforming a predetermined treatment to a wafer transferred and locatedto a predetermined position, an atmospheric transfer equipment disposedin atmospheric air for transferring a wafer in atmospheric air to avacuum transfer equipment, a vacuum transfer equipment disposed within avacuum transfer chamber that connects the atmospheric air and the vacuumprocessing chamber for transferring the wafer received from theatmospheric transfer equipment to the predetermined position within thevacuum processing chamber, and a wafer position sensor disposed near theingress path to the processing chamber for sensing the displacement ofthe transferred wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a plan view showing the vacuum processing deviceaccording to a preferred embodiment of the present invention;

[0014]FIG. 2 illustrates a position sensor;

[0015]FIG. 3 shows the status of the wafer being observed through acamera;

[0016]FIG. 4 illustrates another example of the position sensor; and

[0017]FIG. 5 is an explanatory view illustrating the location of thesensors constituting the position sensor and the location of the wafersbeing transferred.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] The preferred embodiments of the present invention will now beexplained with reference to the accompanied drawings. FIG. 1 is a planview of a vacuum processing device which adopts the present invention.In FIG. 1, an atmospheric transfer unit designated by reference number 1comprises an atmospheric robot 7, cassette stages 6 a, 6 b and 6 c, andwafers 60 a, 60 b and 60 c stored in the cassette stages. One of thecassette stages can be utilized as an orientation alignment unit forcentering or aligning the crystal orientation of the wafer taken out ofthe cassette.

[0019] A buffer chamber is designated by reference number 2, equippedwith a vacuum robot 10 used to transfer the wafer in atmospheric airinto and out of the processing chamber (main processing chamber blocks 3a, 3 b and subsidiary processing chamber blocks 4 a, 4 b), a load lockchamber 8 and an unload lock chamber 9. Reference numbers 5 a, 5 b, 5 cand 5 d denote gate valves for connecting the subsidiary processingchamber block 4 b, main processing chamber block 3 b, main processingchamber block 3 a and subsidiary processing chamber block 4 a to thebuffer chamber 2, respectively.

[0020] Further, reference numbers 30 a and 30 b denote main processingchambers housed within main processing chamber blocks, numbers 40 a and40 b denote subsidiary processing chambers housed within subsidiaryprocessing chamber blocks, and number 60 d denotes a wafer.

[0021] Reference numbers 11 a, 11 b, 11 c and 11 d show position sensorsfor detecting the displacement of the transfer position of the wafers(detailed description of which will appear later). These positionsensors are disposed near the ingress path through which the waferenters and exits the processing chambers (for example, near the entranceof the processing chambers).

[0022] Moreover, in the main processing chamber blocks and thesubsidiary processing chamber blocks, respectively, predeterminedprocesses such as etching or ashing are performed. Vacuum gate valvesand atmospheric gate valves each formed to the load lock chamber 8 andthe unload lock chamber 9 are not shown in the drawing.

[0023] Vacuum gate valves are equipped to both the load lock chamber 8and the unload lock chamber 9 between the buffer chamber 2, andatmospheric gate valves are equipped to both the load lock chamber 8 andthe unload lock chamber 9 between the atmospheric transfer unit 1. Whenthe vacuum processing device is at a process preparation complete status(standby status), the buffer chamber 2, the main processing chambers 3 aand 3 b, and the subsidiary processing chambers 4 a and 4 b are eachmaintained at a vacuum pressure suited for each process. In thefollowing explanation, the processing steps are explained assuming that6 a is used as an orientation (centering) unit.

[0024] The atmospheric robot 7 extends, shrinks or moves its armsideways so as to take out from cassette 6 b one of the wafers storedwithin the cassette 6 b, places the wafer on a stage within thecentering unit 6 a, and retrieves the arm. At this time, the centeringunit corrects the position of the wafer so that it is positionedcorrectly within the processing chamber during thesubsequent-procedures.

[0025] Thereafter, the atmospheric robot 7 accesses the centering unit 6a again, takes out the wafer 60 a having its position corrected,positions the wafer on a stage in the load lock chamber 8 having theatmospheric gate valve opened in advance, and retrieves therefrom. Next,the atmospheric gate valve is closed before the load lock chamber 8 isevacuated, and when the vacuum pressure is reduced to a pressureenabling the chamber to be communicated with the buffer chamber 2, thegate valve between the load lock chamber 8 and the buffer chamber 2 isreleased. Next, the vacuum robot 10 extends its arm to hold the wafer 60a placed inside the load lock chamber 8, and if the wafer is to betreated in the main processing chamber 30 a, the gate valve 5 c isreleased in vacuum, and the wafer 60 a is transferred onto a wafer stagewithin the processing chamber 30 a through the gate valve 5 c. Next, thevacuum robot 10 shrinks and retrieves the arm before the gate valve 5 cis closed, and then the processing of the wafer is performed while theatmosphere within the processing chamber 30 a is set to a condition mostsuitable for processing the wafer.

[0026] The wafer is not only treated within processing chamber 30 a, butcan be transferred to another processing chamber (for example, tosubsidiary processing chamber 40 b) for the next treatment via thebuffer chamber (vacuum chamber) 2. According to this example, after thetreatment in processing chamber 30 a is completed, the gate valve 5 c isreleased so as to enable the vacuum robot 10 to access the processingchamber 30 a and take out the treated wafer, and then the gate valve 5 cis closed again. Next, the gate valve 5 a is released and the vacuumrobot 10 is rotated in position to transfer the wafer into thesubsidiary processing chamber 40 b. The vacuum robot places the wafer onthe stage within subsidiary processing chamber 40 b, and then retrievesthe arm therefrom. Next, the gate valve 5 a is closed and the treatmentof the wafer is started in the subsidiary processing chamber 40 b.Thereafter, if continuous processing is necessary, the above steps canbe repeatedly performed to provide further treatment to the wafer.

[0027] When all the treatment within the vacuum processing chamber iscompleted, the gate valve of the processing chamber is released, thetreated wafer is received by the vacuum robot, and the gate valve of theprocessing chamber is closed before releasing the vacuum gate valve ofthe unload lock chamber 9 which is prepared to receive the wafer with anevacuated inner space. Thereafter, the vacuum robot 10 places the waferon the wafer stage of the unload lock chamber 9, and then retrieves thearm therefrom. Next, the vacuum gate valve of the unload lock chamber 9is closed before introducing air or inert gas into the unload lockchamber 9 so as to increase the inner pressure close to atmosphericpressure. Next, the atmospheric gate valve of the unload lock chamber 9is released, and the atmospheric robot 7 receives the treated wafer andstores the wafer into a predetermined cassette in the cassette stage.

[0028] During this continuous motion, after the wafer is taken out ofthe load lock chamber 8 by the vacuum robot 10, the vacuum gate valve ofthe load lock chamber 8 is closed and air or inert gas is introducedinto the load lock chamber 8 to increase the inner pressure either equalto or close to atmospheric pressure, so as to prepare the chamber forthe next wafer. As for the unload lock chamber 9, after the wafer istaken out from the chamber by the atmospheric robot 7, the atmosphericgate valve is closed to evacuate the interior of the unload lockchamber, so as to prepare the chamber for the next wafer.

[0029] As have been already explained, the wafer 60 a is centered at theorientation alignment (centering) unit 6 a and then handled by theatmospheric robot 7 and the vacuum robot 10 to be sent to various stagesfor various treatments, during which time the wafer is repeatedly placedon or removed from the stages.

[0030]FIG. 2 illustrates a position sensor for detecting the position ofthe wafer being transferred. In FIG. 2, a position sensor is designatedby reference number 11, a viewport mounted on the upper wall of thebuffer chamber 2 for example by vacuum seal is designated by 20, and aTV camera and the like mounted on the viewport 20 is designated by 12.The camera is equipped with an image recognition unit not shown, whichis capable of recognizing the position of the wafer being transferred.

[0031]FIG. 3 is an explanatory view showing the position of the waferbeing observed through the camera. The correct position 601 of the waferpassing the reference line l₁ in the arrow direction is recorded inadvance in the image recognizing unit. Next, the system recognizes thewafer position 602 of the actual wafer being transferred by the vacuumrobot passing the reference line l₁. Thereafter, by comparing these twopositions, the image recognition unit can determine how far the wafer isdisplaced from the correct position 601 when it passed the line.Therefore, by moving the arm of the vacuum robot 10 in the transversedirection with respect to the traveling direction by an amountcorresponding to the detected displacement quantity Δ1, the transferposition of the wafer can be corrected. Further, since the distance oftravel of the wafer from the reference line l₁ to the center stage ofthe processing chamber (distance of movement in the traveling direction)can be computed in advance, the movement within this distance can becontrolled sufficiently by fixed value control.

[0032]FIGS. 2 and 3 illustrate an example where the whole body of thewafer is recognized, but it is not necessary that the whole wafer berecognized, and for example, it is enough to recognize only a portion ofthe arc constituting the outer rim of the wafer.

[0033]FIG. 4 illustrates another example of the position sensor. In thedrawing, reference number 11 denotes a position sensor, 20 a and 20 bare viewports that are fixed by vacuum seal to the upper and lower wallsof the buffer chamber 2, and 13 denotes plural transmission type opticalsensors that constitute the position sensor, wherein sensors 13 are setto detect the outer rim (edge) of the passing wafer, for example. Otherthan the transmission type optical sensors, the sensors 13 can bereflecting type optical sensors or capacitance type sensors.

[0034]FIG. 5 is an explanatory view illustrating the location of thesensors 13 constituting the position sensor, and the position of thewafer being transferred. As shown in the drawing, plural sensors aredisposed at plural points, respectively. For example, three sensors arelocated at point A, point B and point C, respectively. The illustratedexample shows the sensors to be disposed in an arc along the outer rimof the wafer, but they can also be arranged linearly. Further, 611 showsthe correct position through which the wafer passes the reference linel₂ in the arrow direction, and 612, 613 and 614 each show the actualposition of the wafer being transferred along the arrow direction.

[0035] Similar to the example illustrated in FIG. 3, when the waferpasses the reference line at a location displaced by Δ1 from the correctposition, the sensor located at point A detects the wafer first.Thereafter, the sensor located at point B detects the wafer, and thenthe sensor located at point C does the same.

[0036] At first, when the wafer is transferred to the wafer position612, the sensor located at point A detects the outer rim of the wafer.Thereafter, when the wafer is transferred to wafer position 613, thesensor located at point B detects the outer rim of the wafer. Finally,when the wafer is transferred to wafer position 614, the sensor locatedat point C detects the outer rim of the wafer.

[0037] When the sensor located at point C detects the outer rim of thewafer, the virtual position of the portion of the wafer that passedsensor A is located at point A′ which is advanced by distance Vt1 frompoint A, assuming that time t1 has passed from detection and that thetravel speed is V. Further, the virtual position of the portion of thewafer that passed sensor B is located at point B′ which is advanced bydistance Vt2 from point B, assuming that time t2 has passed fromdetection and that the travel speed is V.

[0038] When the virtual positions A′ and B′ are thus computed, based onthese positions and the position of known point C, the center positionof the wafer (circular wafer) can be computed. Further, based on thiscomputed position, the displacement amount Δ1 of the wafer can becomputed.

[0039] Thereafter, the arm of the vacuum robot 10 is moved in thetransverse direction for a distance corresponding to the computeddisplacement amount Δ1, thereby correcting the transfer position of thewafer to the proper position. Since the distance of movement of thewafer from reference line l₂ to the stage center of the processingchamber (distance of movement in the traveling direction) can becomputed in advance, the movement can be controlled sufficiently basedon fixed values. Though the distance of movement of the wafer fromreference line l₂ to the stage center of the processing chamber(distance of movement in the traveling direction) includes an error δcorresponding to the displacement amount Δ1 (when radius of wafer isrepresented by R, δ=R−(R2−Δ1²)^(1/2)), the error is so small that it canbe ignored.

[0040] As explained, according to the present embodiment, sensors 11a-11 d for detecting the displacement of the transfer position aredisposed in front of each processing chamber block so as to detect thedisplacement of the wafer directly before placing the wafer onto thestage inside the processing chamber. Thereafter, by controlling thetransfer robot based on this detected result to correct thedisplacement, the wafer can be placed precisely at the determinedposition on the stage.

[0041] In the above example, the sensors for sensing the displacement ofthe wafer are disposed on the buffer chamber side of the gate valve ofeach processing chamber block, but the sensors can be disposed on theprocessing chamber side of the gate valve if necessary. Even further,the sensors can be positioned near the center of the buffer chamber.

[0042] Since according to the present embodiment the displacement of thewafer is detected or computed at the final step of the wafer transfer toeach processing chamber, and the displacement occurring as a result ofaccumulated transfer errors is corrected at the last stage, the wafercan be transferred and mounted to the determined position on the stagewithin the processing chamber with high accuracy. The transfer accuracyperformed by an operator based on visual observation is at best{fraction (3/10)} mm to {fraction (2/10)} mm, but the present embodimentenables to improve the accuracy by about ten times, or to the level ofapproximately {fraction (2/100)} mm. Further, the sensors are notnecessarily disposed near all the processing chambers (the mainprocessing chambers and subsidiary processing chambers). For example, ifthe process performed within a certain processing chamber does notrequire highly accurate positioning, there is no need to dispose sensorsfor that processing chamber.

[0043] According to the present invention, the displacement of thetransfer position of the wafer is detected and corrected directly priorto the final stage, so the wafer can be correctly transferred andpositioned with high accuracy.

What is claimed is:
 1. A vacuum processing device comprising: a vacuumprocessing chamber for performing a predetermined treatment to a wafertransferred to and located on a predetermined position; an atmospherictransfer equipment disposed in atmospheric air for transferring a waferin atmospheric air to a vacuum transfer equipment; a vacuum transferequipment disposed within a vacuum transfer chamber connecting theatmospheric air and said vacuum processing chamber, for transferring thewafer received from said atmospheric transfer equipment to saidpredetermined position within said vacuum processing chamber; and awafer position sensor disposed near an ingress path leading to saidvacuum processing chamber for sensing the displacement of said waferbeing transferred.
 2. A vacuum processing device comprising: a vacuumprocessing chamber for performing a predetermined treatment to a wafertransferred to and located on a predetermined position; an atmospherictransfer equipment disposed in atmospheric air for transferring a waferin atmospheric air to a vacuum transfer equipment; a vacuum transferequipment disposed within a vacuum transfer chamber connecting theatmospheric air and said vacuum processing chamber, for transferring thewafer received from said atmospheric transfer equipment to saidpredetermined position within said vacuum processing chamber; a waferposition sensor disposed near an ingress path leading to said vacuumprocessing chamber for sensing the displacement of said wafer beingtransferred; and a correction means for correcting the position of saidwafer based on the result of detection performed by said wafer positionsensor.
 3. A vacuum processing device according to claim 1 or claim 2,wherein said wafer position sensor comprises at least three opticalsensors for sensing the rim position of the wafer being transferred bythe vacuum transfer equipment.
 4. A vacuum processing device accordingto claim 1 or claim 2, wherein the initial positioning of said wafer isperformed using a unit disposed in atmosphere, and the displacement ofsaid wafer is detected using a unit disposed directly before the stagewithin said vacuum processing chamber.
 5. A vacuum processing method fortransferring a wafer to a predetermined position within a vacuumprocessing chamber using a transfer equipment and performing apredetermined treatment to said wafer in said vacuum processing chamber;said method comprising: an atmospheric transfer step of transferring thewafer in atmospheric air to a vacuum transfer equipment using anatmospheric transfer equipment disposed in atmospheric air; a vacuumtransfer step of transferring the wafer received from said atmospherictransfer equipment to said predetermined position within said vacuumprocessing chamber using a vacuum transfer equipment disposed within avacuum transfer chamber connecting the atmospheric air and said vacuumprocessing chamber; and a step of detecting the displacement of saidwafer being transferred using a wafer position sensor disposed near aningress path leading to said vacuum processing chamber.
 6. A vacuumprocessing method for transferring a wafer to a predetermined positionwithin a vacuum processing chamber using a transfer equipment andperforming a predetermined treatment to said wafer in said vacuumprocessing chamber; said method comprising: an atmospheric transfer stepof transferring the wafer in atmospheric air to a vacuum transferequipment using an atmospheric transfer equipment disposed inatmospheric air; a vacuum transfer step of transferring the waferreceived from said atmospheric transfer equipment to said predeterminedposition within said vacuum processing chamber using a vacuum transferequipment disposed within a vacuum transfer chamber connecting theatmospheric air and said vacuum processing chamber; a step of detectingthe displacement of said wafer being transferred using a wafer positionsensor disposed near an ingress path leading to said vacuum processingchamber; and a step of correcting the position of said wafer based onthe displacement being detected.
 7. A vacuum processing method accordingto claim 5 or claim 6, wherein the step of detecting the displacement ofsaid wafer comprises a step of detecting the rim position of said waferbeing transferred in the vacuum transfer step using at least threeoptical sensors.
 8. A vacuum processing method according to claim 5 orclaim 6, wherein initial positioning of said wafer is performed inatmosphere, and the displacement of said wafer is detected directlybefore the stage within said vacuum processing chamber.